The action of many hormones requires their interaction with specific cell surface receptors that are coupled by the guanine nucleotide-binding protein Gs to stimulation of adenylyl cyclase. Expression of hormones, receptors, or Gs molecules with altered biological activity can result in gain or loss of hormone action. This protocol examines the molecular basis for altered hormone action in signal transduction pathways that utilize Gs protein as a signal transducer. These disorders include pseudohypoparathyroidism type 1a and McCune Albright syndrome due to altered expression or function of Gs, hypoparathyroidism due to defects in the calcium-sensing receptor or PTH gene, and short stature due to defects in the growth hormone-releasing hormone receptor. Biochemical and clinical characterization of the patient's phenotype facilitates a laboratory-based approach to elucidating the molecular mechanism of disease. Over the past year we have evaluated the clinical and endocrine characteristics of patients with PHP type 1a and McCune Albright syndrome, and have continued to refine the genotype-phenotype relationship of these genetic syndromes. Perhaps most significant has been our identification of a male with McCune Albright who appears to be the first example of non-mosaic McCune Albright syndrome.